Heat pump



March 8, 1949. E. N. KEMLER. 2,463,881

HEAT PUMP Filed July 6, 1946 3 Sheets-Sheet 2 .15 n 23 FIG. 4

canmssson 53 rms 57 sscono 65' OONDEASER counsussn 110' a) arr 7 "PF sscono EVAPO- RATOR arr: v Mr.

I V I v INVENTOR. 47 Y 52 BY EMORY N. KEMLER CMPRESSOR ATTORNEYS Patented Mar. 8, 1949 HEAT PUMP Emory N. Kemler, Birmingham, Ala., assignor to Muncie Gear Works, Inc., Muncie, Ind., a corporation of Indiana.

Application July 6, 1946, Serial No. 681,635

The heat pump, as its name implies, is a device for pumping thermal energy, or heat, from one temperature to some higher temperature. We

10 Claims. (01. 62-129) know from observation that the flow of heat normally or naturally takes place from a given tem perature to a lower temperature. To cause the flow to take place in a reverse direction requires the use of a mechanical device to supply the work required to raise the temperature of the medium and thus pump a given quantity of heat from the lower to the higher temperature. .This is dependent upon the diflerence in the temperature levels just as the power to pump a given quantity of water is dependent on the difference in heads or water levels. Anything which will increase this difference in heat level will decrease the power or energy required and, therefore, will pumps by staging the elements of the heat exchange devices of a refrigerating cycle so as to increase their eiiectiveness in causing a flow of heat to and from a moving fluid medium.

Time is a factor in heat transfer; hence, as air or water is traveling it is heated or cooledmore efiiciently by a series of staged condensers or a series of evaporators, or both, each operating at successively increased or decreased temperatures, as the case may be, than can be don by a single unstaged unit. Staging accomplishes the end result with less expenditure of energy and accordingly with a higher coeflicient performance.

The main objects of this invention are to provide improvements in the combination and arrangement of the elements of a refrigeration cycle in a system particularly" adapted for its use as a heat pump; to provide improved means for staging the condenser and evaporator functions of heat exchange devices with a minimum of complication, or other difficulties affecting the performance of the refrigeration cycle; and to provide an improved form of heat pump construction particularly adapted for use in transferring heat from one fluid medium to another for the purpose of conditioning the air of a room.

This invention is herein disclosed by means of which both the condenser and evaporator are staged.

Fig. 2 is a chart showing. comparatively the co- 2 efllcients of performance of a staged unit and a standard unstagedunit of heat pump apparatus based on comparable data.-

Fig. 3 is a diagrammatic view of a heat pump apparatus in which the evaporator and the condenser units are stagedinaccordance with this invention. 7

'Fig. 4 is a diagrammatic view of a similarly staged heat pump with illustrative temperature indicia noted thereon at various points 'to correspond with its operation as an air heating plant.

Fig. 5 is a similar diagrammatic representation of a refrigeration cycle hookup, wherein certain condenser units and certain evaporator units are 1 arranged in a plurality of separate refrigeration cycles coordinated with each other as to performance, and. wherein the condenser units and the evaporator units are each staged in their relation to the source medium and heat medium, respectively.

Fig. 6 is a somewhat diagrammatic detail showing a suitable modified arrangement for connecting staged condensers.

Figs. 7 and 8 are further diagrammatic illustrations of modifications of'this detail.

Fig. 9 shows a form of trap suitable for use in connection with staged condensers in the arrangements illustrated in Figs. 3', 4 and 8.

The advantages of staging will best be understood from ,a consideration of the temperature changes that occur in an apparatus of this kind, I

as illustrated schematically in Figure 1 in which the rectangles l and 2 represent separate condenser unit stages and the rectangles 3 and 4 represent separate evaporator unit stages.

. In Fig. 1 the line 5 indicates the temperature I of higher temperature to a place of lower temperature, the evaporator stage 3 must, in the heating cycle of the pump, be operated at a temperature, indicated by the line 1, which is somewhat lower than the initial temperature of the heat source medium; and the evaporator stage 4 must be operated at a temperature, represented by the line 8, which is somewhat lower than the temperature of the source medium received from stage 3, in order that heat will flow from this source medium to the refrigerant at each stage.

Similarly, in order that. heat will flow from the-- condenser stages to the room air or other medium to which the heat is to be delivered by the pumpe the condenser stages must be operated at temperatures that are in each stage higher than? the desired delivery temperature of that air.

, The direction of flow of the media represented by the lines 5 and 6 is from left to right of Fig. 1

and it will be noted that the air to be heated,

called air from the house in the diagram, has

'These temperatures are indicated on the chart of Fig. 1 by the lines 9 and It as the corresponding temperatures of the refrigerant in the condenser.

In the-lower part of the diagram of Fig. 1 the situation in the evaporator is shown. The outside air or water, whichever is the source of heat, is supplied to the first evaporator and as it passes through the evaporator heat is extracted from it, resulting in a temperature drop. In order to have the heat flow from this source to the refrigerant, it is necessary to have the temperature of the refrigerant in the evaporator lower at all stages than the temperature of the air or water that is being used as a source of heat.

As is indicated in this diagram, the actual temperature distance through which heat must be pumped will be from slightly below the temperature of the refrigerant in the evaporator to slightly above the temperature of the refrigerant in the condenser.

Consideration of the chart shown in Fig. 1, shows that, by dividing the condenser-evaporator units into stages, these units can be operated at successively difierent temperatures and always provide an adequate margin of difference in temperature between the air that is flowing through the condensers and th temperature of the refrigerant to insure a continuous flow of heat between the two. Thus there is a considerable saving of power when the mechanical arrangement is such as to provide separate means for controlling these condenser and evaporator temperatures.

In order to provide the temperature steps in successive condenser and evaporator units, a multicylinder compressor is used with a separate cylinder in refrigeration cycle relation to each stage, but the individual condenser stages and evaporator stages may be combined in various ways. For example, one cylinder may operate condenser l and evaporator 3 of Fig. 1, and another cylinder may operate condenser 2 and evaporator 4. In this case the temperature range of the first cylinder is shown in Fig. 1 by line A and the temperature range in the second cylinder is shown by line B. If condenser l is coupled with evaporator 4, and condenser 2 is coupled with evaporator 3, then the temperature range of the respective cylinders is shown by lines 0 and D of Fig. 1.

Fig. 2 shows comparative differences in coefilcient of performance at different suction temperatures at the intake of the compressor. The curve I I shows in the vertical scale the coeflicient of performance corresponding to the suction temone constant temperature and that the evapora- .4 perature indicated in the horizontal scale on the assumption that the condenser is maintained at tor is maintained at another. The curvel2 shows the po ng improvement in the coefficient' f i r of performance that is'a'ccom'plished by stagin "g5 The same general principles; which make condenser staging desirable apply to evaporator stag- -ing. When the outside air or water, which is used 7 as a sourceof heat, passes through the evaporator its temperature falls as the heat is abstracted from it. In order to getthis heat to flow from the heat source medium to the evaporator, it is necessary to maintain the evaporator at a temperature lower than the lowest temperature of the source medium. flowing through the evaporator. If the evaporator is staged or divided into two or more parts, thetemperature which must be maintained in the first evaporator, to maintain the same rateof'heat flow, may be higher than the temperature in the succeeding evaporator stage, and so on; thereby decreasing the average temperature rangethrough which the heat must 7 a better coefflcient'of performance for the same I quantity of heat pumped.

The same general principles apply to house coolingas to house heating. In the case of heating, the air going to the house is passed over the condensers; and in the case of cooling, the air going to the house is passed over the evaporators. All of the advantages of staging for heating apply to cooling,the only difference being in quantitative requirements. Qualitatively there is no difference.

The foregoing discussion has been concerned with power requirements. Under some conditions it is possible that weight-saving, space-saving, cost or some other mechanical or economic result would necessitate reduction of size of the conorder to get better load balancing. One of the problems of good heat pump design is to get proper balance between the condenser and evaporator surfaces and compressor capacity.

In the mechanical system shown in Figure 3, the condenser is divided into three stage units l3, l4 and I5 and the evaporator is correspondingly divided into three stage units I6, I! and I8 and the compressor I9 is provided with separate cylinders 20, 2| and 22 connected in refrigeration cycle relation to these respective stages. An even distribution of cylinders is not necessary. The best arrangement will depend upon the relative distribution of heat transfer surfaces. In this case, each of these compressor cylinders or groups of cylinders would supply a particular stage of both the evaporator and the condenser.

The cylinder 20 sucks the refrigerant from the evaporator I6 through pipe 23, compresses it and discharges it through pipe 24 to condenser unit l3. Similarly. compressor cylinder 2! serves evaporator unit I! and condenser unit [4 through pipes 23.l and 2H; and cylinder 22 serves evaporator unit l8 and condenser unit l5 through pipes 23.2 and 24.2. t

In this system, as shown in Fig. 3, a single receiver 25, through pipe 26 and individual expansion valves 21, 28 and 29, supplies refrigerant at properly regulated pressures corresponding to the temperatures or evaporators I0, I! and l8.

Inasmuch as the condenser units are operated at successively increasing temperatures, it is not practical to connect their discharge ends to a common discharge line running to the receiver 25 without making adequate provision for the fact that these units l3, l4 and I5 operate at diflerent pressures.

In Fig. 3 condenser unit I3 is connected by pipe 30' and trap 3| to the inlet pipe J or the condenser unit l4 which, in turn, by pipe 32 through trap 33 with the inlet pipe 24.2 of condenser i5 and this discharges into the receiver 25. The traps 3i and 33 may be of the type which is normally closed against the flow of gas or vapor and opens at intervals to discharge accumulations of condensate. There are, of course, many forms of such valves of which the float valve shown in Fig. 9 might be said to be generally representative.

The mode of connection, as shown in Fig. 3, makes proper compensation for the fact that the condenser units are operated at progressively different temperatures and pressures. The volume of condensate discharged by the traps is relatively small compared to the flow of vapor with which it mixes in the pipes 24.l and 24.2 and under this arrangement there would be noharm done if some of the condensate should flash back into vapor form on its way to the receiver.

In the form shown in Fig. 3 water is used as a source of heat in the heating season and also as a dump for heat in the cooling season.

To this end each condenser unit ll, l4 and I5 is served by a water coil 34, 34.i and 34.2 respectively and each evaporator unit i5, I1 and I8 is served by a water coil 35, 35.l and 35.2 respectively. Water is supplied from an inlet pipe 36 through a three-way valve 31, either to the water coils of the condenser units through pipe 38 or to the water coils of the evaporator units through pipe 38.

Water coils of the evaporator units are preferably end to end with each other and discharge through pipe 40 to a drain 4!. Thewater coils of the condenser units are, however, connected in manifold relation both to the inlet pipe 38 and to the outlet pipe 42 which leads to thedrain 4i. This arrangement ofthe water coils assures that the maximum amount of heat will be extracted from the water during its passage through the evaporators in theheating season and that the maximum amount oi. heat will be dumped by the condensers into the cooling water system during the cooling season.

In devices of this kind the air flowing to the room that is to be heated by the heat pump is directed over the condensers during the heating season, as indicated by the arrows 43 and fan 44; and during the cooling season such air flow is directed over the evaporator coils, as is indicated by the arrows "and fan 48, by means of appropriate duct work and baflie means which are not illustrated in Fig. 3 but are well understood inthis art.

A specific example of such duct work is shown in Patent No. 2,401,890, issued to me jointly with others on June 11, 1946. f

In operation during the heating season, the current of air indicated by the arrows 43 is the fluid medium into which the heat pump dumps heat for the purpose of heating the building into which air flows; and the water flowing through the water coils 35 oi the evaporator units is the is extracted by the evaporators from the house conditioning air current, which is caused to flow is connected in heat transfer relation to the evaporators as represented by arrows 45 and is carried by the refrigerant to the compressor and then to the condenser where it is dumped into the water circulating in the coils 34 and discharged from the building.

In the diagrammatic drawing of Fig. 4 only those parts of the system of Fig. 3 that are used during the heating seasonare shown and indications of temperatures are shown at various places for the purpose of illustrative representation of relative temperatures that might prevail in diiferent parts of the apparatus under certain assumed conditions during the heating season. It will be understood that under these circumstances the air to be conditioned is directed into heat exchange relation with the condensers and excluded from the evaporators.

' In this example, the connections between the condensers and their respective cylinders are slightly changed from the arrangement shown in Fig. 3 so as to reverse the sequence of the flow of condensate through the condenser units It, l 4

- and [5 on its way to the receiver.

But otherwise the structure of these two forms is substantially the same.

In Fig. 5, a diagrammatic representation is shown of an arrangement in which each condenser unit is connected in a separate refrigeration cycle, each with its respective evaporator, receiver and expansion valve so as to have the advantage of staging while eliminating the disadvantage of traps or other devices for compensating for differences of pressure in the successive condensers whereby each condenser and each evaporator is indpendent of any other. In this arrangement, the compressor cylinder 41 operates the refrigeration cycle which comprises the condenser 48, receiver 49, expansion valve and evaporator 5|; and the compressor cylinder 52 operates the refrigeration cycle which comprises and evaporator 56.

The air or water flow, indicated by the arrow 51, is in the direction in which it first traverses the condenser 48 and then the condenser 53; and

the air or water flow over the evaporators, indicated by the arrow 58, is such that it first traverses the evaporator 56 and then the evaporator 5!. In such arrangement, the temperature range in each refrigeration cycle may be of the same extent, although the actual temperatures may be different, being stepped up in successive stages so as to most efliciently accomplish the transfer of heat to the moving air current.

In a condenser arrangement comprising staged units connected in series arrangement in the same cycle of refrigerant flow, compensation for differences in the pressures in successive con-- denser units can be had by an arrangement such as is illustrated in Fig. 6, wherein the'second or higher pressure condenser unit 59 has its outlet end connected with the inlet end of the first or low pressure condenser unit 60 by a pipe 6| which has either a trap (not shown) or a capillary tube 82 interposed therein .to assure that only'liquid the condenser 53, receiver 54, expansion, valve l5 7 condensate may pass through. In this form, the second condenser 58 has an inlet pipe .3 connected to its respective compressor and the first condenser has an inlet pipe I! connected to its respective compressor cylinder but, only the lowest pressure condenser unit 60 has its outlet pipe I connected to the common receiver. The air flow in this case is indicated by the arrow 08 for the heating season arrangement.

In Fig. 7, a modified arrangement of staged condensers 61 and 88 is provided by having separate inlet pipes 88 and" leading from separate compressor cylinders to the respective condenser stages and having the outlet pipe of the second condenser 88 connected, through a capillary tube II and a heat exchanger I2, to the outlet pipe ill of condenser 81 and the common pipe 11 leading to the receiver. The heat exchanger 12 may be controlled thermostatically or by pressure-actuated means (not shown) to cool the outi'lowing condensate from the second condenser to a temperature at which it will not flash into vapor but will remain liquid on mixing with the condensate from the first condenser.

A similar arrangement to this is shown in Fig. 8, wherein the capillary tube is replaced by a trap 13 which may be of the form shown in Fig. 9 and which comprises a valve ll actuated by a lever I controlled by a float 18 to insure that only liquid condensate will be discharged from the condenser 88. In either of the forms shown in Figs. 7 and 8, the function of the heat exchanger is to equalize the condensate temperatures and avoid having one of them flash into vapor as it merges with the other.

It will be understood that numerous details of the specific constructions herein shown and described may be altered or omitted without departing from the spirit of the invention defined by the following claims.

I claim:

1. A heat pump, comprising, in a combination utilizing a refrigerant to transfer heat from one fluid medium to another of different temperature, a series of condensers, a compressor havingseparate means for supplying the refrigerant to the individual condensers at successively increasing temperatures, a series of evaporators each coactingcyclically with said compressor means and adapted to operate at successively decreasing temperatures with respect to one another, expansion means between said condensers and evaporators, each of said condensers and evaporators comprising a refrigerant coil having a water passage and an air passage in heat exchange relation to the refrigerant coil, and valve means for directing a flow of water alternatively to said condensers and said evaporators.

2. A heat pump, comprising, in a combination utilizing a refrigerant to transfer heat from one fluid medium to another of different temperature, a series of condensers, a compressor having separate means for supplying the refrigerant to the individual condensers at successively increasing temperatures, said condensers being connected in series relation to theflow of refrigerant therethrough with vapor traps interposed between successive condensers, a series of evaporators each coacting cyclically with said compressor means and adapted to operate at successively decreasing temperatures with respect to one another, expansion means between said condensers and evaporators, each of said condensers and evaporators comprising a refrigerant coil having a water passage and an air passage in heat exchange relation l0 utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual condensers at respectively different pressures, evaporator means coacting in the refrigerant cycle with said condensers and compressor, a passage connecting the outlet of the higher pressure condenser with the inlet of the lower pressure con- 20 denser, a vapor trap in said passage, and expansion means in the refrigerant cycle between the outlet of said lower pressure condenser and said evaporator means.

4. A heat pump, comprising, in a combination utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual condensers at respectively different pressures,

evaporator means coacting in the refrigerant cycle with said condensers and compressor, a passage connecting the outlet of the higher pressure condenser with the outlet of the lower pressure condenser, a heat exchanger in said passage, and

expansion means in the refrigerant cycle between the outlet of said lower pressure condenser and said evaporator means.

.5. A heat pump, comprising, in a combination 0 utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual condensers at respectively different pressures,

evaporator means coacting in the refrigerant cycle with said condensers and compressor, a passage connecting the outlet of the higher pressure condenser with the inlet of the lower pressure condenser, a capillary vapor trap in said passage, and expansion means in the refrigerant cycle between the outlet of said lower pressure condenser and said evaporator means.

6. A heat pump, comprising, in a combination utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual 00 condensers at respectively different pressures,

evaporator means coacting in the refrigerant cycle with said condensers and compressor, a passage connecting the outlet of the higher pressure condenser with the outlet of the lower pressure 65 condenser, a vapor trap and a heat exchanger in said passage, and expansion means in the refrigerant cycle between the outlet of said lower pressure condenser and said evaporator means.

7. A heat Pump, comprising, in a combination utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual condensers at respectively different pressures, evaporator means coacting in the refrigerant cycle with said condensers and compressor, a passage connecting the outlet of the higher pressure condenser with the outlet of the lower pressure condenser, a capillary vapor trap and a heat exchanger in said passage, and expansion means in the refrigerant cycle between the outlet of said lower pressure condenser and said evaporator means.

8. A heat pump, comprising, in a combination utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual condensers at respectively difierent pressures, evaporator means coacting in the refrigerant cycle with said condensers and compressor, a passage connecting the outlet of the higher pressure condenser with the inlet of the lower pressure condenser at the point between said lastnamed inlet and its respective compressor means, a vapor trap in said passage, and expansion means in the refrigerant cycle between the outlet of said lower pressure condenser and said evaporator means.

9. A heat pump, comprising, in a combination utilizing a refrigerant cycle to transfer heat from one fluid medium to another, a pair of condensers, each having an inlet and an outlet for the refrigerant, a compressor having separate means for supplying the refrigerant to the individual condensers at respectively different pressures, evaporator means coacting in the refrigerant cycle with said condensers and compressor, a 35 compressor means for said lower pressure condenser, and expansion means in the refrigerant cycle between the outlet of the lower pressure condenser and said evaporator means.

10. A heat'pump, comprising, in a combination utilizing a refrigerant to transfer heat from one fluid medium to another of diiferent temperature, a series of condensers, a compressor having separate means for supplying the refriger ant to the individual condensers at successively increasing temperatures, a series of evaporators each coacting cyclically with said compressor means and adapted to operate at successively decreasing temperatures With respect to one another, expansion means between said condensers and evaporators, each of said condensers and evaporators comprising a refrigerant coil having a water passage and an air passage in heat exchange relation to the refrigerant coil, means connecting said evaporator water passages in series relation to each other, means connecting said condenser water passages in parallel relation to each other, and valve means for directing a flow of water alternatively to said condensers or said evaporators.

EMORY N. KEMLER.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 2,008,407 Stoever July 16, 1935 FOREIGN PATENTS Number Country Date 338,283 Germany June 15, 1921 

